Photosystem I coordinates more than 90 chlorophylls in its core antenna while achieving near perfect quantum efficiency. Low energy chlorophylls (also known as red chlorophylls) residing in the antenna are important for energy transfer dynamics and yield, however, their precise location remained elusive. Here, we construct a chimeric Photosystem I complex in Synechocystis PCC 6803 that shows enhanced absorption in the red spectral region. We combine Cryo-EM and spectroscopy to determine the structure - function relationship in this red-shifted Photosystem I complex. Determining the structure of this complex reveals the precise architecture of the low energy site as well as large scale structural heterogeneity which is probably universal to all trimeric Photosystem I complexes. Identifying the structural elements that constitute red sites can expand the absorption spectrum of oxygenic photosynthetic and potentially modulate light harvesting efficiency.
Organizational Affiliation:
School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287-1604, USA.
Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, 85287, USA.
Department of Chemistry, Kansas State University, Manhattan, KS, 66506, USA.
John M. Cowley Center for High Resolution Electron Microscopy, Arizona State University, Tempe, AZ, 85287, USA.
Center for Innovations in Medicine at the Biodesign Institute, Arizona State University, Tempe, AZ, 85287, USA.
Department of Physics, Kansas State University, Manhattan, KS, 66506, USA.
School of Molecular Sciences, Arizona State University, Tempe, AZ, 85287-1604, USA. yuval.mazor@asu.edu.
Biodesign Center for Applied Structural Discovery, Arizona State University, Tempe, AZ, 85287, USA. yuval.mazor@asu.edu.
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